This invention relates to a motor vehicle suspension system of the type having a damper with a rotatable member providing different damping positions in different rotational positions, a motor to drive the rotatable member, a feedback apparatus for indicating the rotational position of the rotatable member and a control responsive to the feedback apparatus and other inputs for selecting a desired rotational position and controlling the motor to drive the rotatable element thereto. It particularly relates to such a system in which the rotatable member, motor and feedback apparatus are all included within the damper.
In such a suspension system, the feedback apparatus may comprise a plurality of contact pads, one for each position of the rotatable member and separated by insulating regions, and an electric circuit including a contact member moving over the contact pads so as to generate an output voltage in a first voltage range when the rotatable member is between the positions and a second voltage range when the rotatable member is in one of the positions. The apparatus may repeatedly sample the output voltage to detect changes therein between the voltage ranges. A counter may be incremented with each valid transition of the output voltage from the first voltage range to the second voltage range, with the count of the counter indicating the position of the rotatable member. Means may be provided for selecting one of the rotational positions and stopping the motor when the counter indicates the selected rotational position.
If the rotatable member has a comparatively large number of rotatable positions, such as eight, for example, each rotational position will subtend a comparatively small arc of a complete rotation of the rotatable member: for example, 15 degrees. In order to stop the rotatable member within this 15 degree arc, the motor must be deactivated at the first detection of the desired contact pad, as indicated by a transition in the output voltage from the first voltage range to the second voltage range. However, the contact member is liable to bounce following its first contact with the contact pad; and this will cause the output voltage to alternate between its first and second voltage ranges for some period of time before settling into the second voltage range. However, it is undesirable for the counter to be incremented more than once for each new rotational position of the rotatable member.